This invention relates to a fuel supply system for an engine and more particularly to an emergency starting fuel supply system.
Charge forming systems for most internal combustion. engines provide some form of fuel enrichment for starting and/or for cold running. This is particularly true in conjunction with two cycle crankcase compression internal combustion engines due to the long distance that the fuel must travel from its introduction into the engine and its delivery to the combustion chambers. As is well known, the fuel air charge is normally delivered to the crankcase chambers of the engine and then must travel through the scavenge passages to the combustion chambers. Under low temperatures, the fuel condensation in this circuitous path can require considerable enrichment. Of course, this problem is also true with respect to four cycle engine and two cycle engines wherein the fuel is introduced somewhere other than the crankcase chamber.
In one form of starting or cold running enrichment system, in addition to the main fuel pump of the engine there is provided an auxiliary fuel pump and an auxiliary fuel control valve which supply fuel to the engine for these abnormal conditions. Of course, the use of such added pumps and valves considerably complicates the system and may, in sole instances, give rise to considerable problems if there is a failure. Specifically, if the additional fuel pump and/or additional fuel valve become inoperative then starting of the engine may be difficult or impossible and cold running can be irregular at best.
Although arrangements have been provided for bypassing the cold enrichment system in the event of some failure, such systems still require the supply of additional fuel for starting. These systems normally rely on the main pressure pump for the supply of additional fuel and this pump may not under all circumstances provide adequate fuel, particularly for initial priming.
It is, therefore, a principal object of this invention to provide an improved and simplified fuel supply system for cold starting or cold running of engines.
It is a further object of this invention to provide an improved, simplified and highly effective auxiliary cold starting or cold running enrichment system that will be highly effective and quite simple in its operation.
It is a further object of this invention to provide such an auxiliary enrichment mechanism which will not adversely effect the running if the engine if it is inadvertently left in position when the engine is running and the enrichment is not required.